Lee Woo Young

The author is an HCMC distinguished professor at the Korea Institute for Advanced Study.

Readers have long left traces of their thoughts in the margins of books - a practice known as marginalia. Writers and scholars such as Michel de Montaigne, Isaac Newton and Charles Darwin were all fond of this habit. But what might be the most extraordinary marginal note in human history?

In the 17th century, French mathematician Pierre de Fermat (1601 - 1665) filled the margins of Diophantus's ancient work "Arithmetica" with his own comments. After Fermat's death, his son noticed that these annotations seemed unusual and decided to publish the book in 1670, including his father's notes. One of them, later known as "Fermat's Last Theorem," carried an infamous remark: "there was not enough space in the margin to include the proof."



That cryptic message spurred generations of mathematicians to seek the missing proof. For more than three centuries, many wept in frustration, yet their failures gave rise to profound advances in number theory. The theories that emerged from this pursuit profoundly influenced the course of modern civilization. By that measure, Fermat's marginal note may well be the most remarkable ever written.

I once left a few such notes myself while reading Bertrand Russell's "An Essay on the Foundations of Geometry" (1897). Preparing for a recent lecture, I took the old volume off the shelf and found one of my faded notes marked with a question mark. Curious about what had prompted it, I reread the passage. Russell had written, "At first he cut away the flabby shell, and at last his cleverness cut away God himself."

Back when I first read it, I had no idea who "he" referred to. This time, the meaning struck me - the subject was none other than our own self, the restless creator of artificial intelligence. The old note had been waiting for decades to awaken its meaning.

Notes in the margins can reignite old questions, transport us back through memory or, as in Fermat's case, accompany humanity on a long journey of discovery. In the digital age, the faded handwriting in the margins of old paper books feels more intimate than ever - a quiet light lingering between the lines of time.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.